1. Field of the Invention
The present invention relates to an angular rate detecting device for detecting an angular rate which is produced when a mobile body such as a motor vehicle moves.
2. Description of the Prior Art
LSI circuits and microcomputers which can execute very complex arithmetic operations have been developed in recent years as a result of modern semiconductor developments. Control devices using such LSI circuits and microcomputers have also been developed to perform various sophisticated control functions. These control devices have been improved and are now so reliable that they can operate properly in severe adverse environments such as on motor vehicles.
One of recent major efforts directed to the motor vehicle technology is the development of a suspension control system which improves the riding comfort and stable maneuverability of a motor vehicle. According to a conventional suspension control system, various disturbances, such as a roll and a pitch, which act on a motor vehicle while it is being driven are detected by sensors installed on the motor vehicle, and the spring constants, damping forces, and damping strokes of the suspensions on the motor vehicle are varied depending on the detected disturbances, thereby maintaining desired levels of riding comfort and maneuvering stability of the motor vehicle.
One conventional suspension control system will be described below with reference to FIG. 1 of the accompanying drawings. The suspension control system includes an electronic controller 1 which is supplied with detected information from a number of sensors mounted on a motor vehicle. Based on the supplied information, the electronic controller 1 operates actuators disposed in respective shock absorbers 2 of suspensions associated with respective road wheels, for varying damping forces produced by the shock absorbers 2. For example, the suspension control system performs anti-squat, anti-dive, anti-roll, and anti-bounce functions. More specifically, the anti-squat function prevents the rear end of the motor vehicle from being lowered during hard acceleration based on detected information from a throttle position sensor 3 and vehicle speed sensor 4. The anti-dive function is effective to resist the nosing-down of the front end of the motor vehicle during braking or engine braking based on detected information from a brake switch 5 and the vehicle speed sensor 4. The anti-roll function resists rolling of the motor vehicle, caused by a steering action, based on detected information from a steering sensor 6 and the vehicle speed sensor 4. The anti-bounce function responds to detected information from a road condition sensor 7 and the vehicle speed sensor 4 to prevent the motor vehicle from pitching in rough road conditions.
Another suspension control system includes, in addition to the sensors described above, an acceleration sensor, a clutch sensor, a parking brake switch, and a door switch to produce other information to be supplied to the electronic controller.
Generally, a suspension with variable damping forces is controlled for a softer damping setting if more riding comfort is desired, and for a harder damping setting if more maneuvering stability is desired. According to the conventional suspension control systems, if a control mode is selected for more maneuvering stability than riding comfort, many phenomena such as a change in the vehicle speed, a change in the steering angle, and a change in the road condition, which are responsible for disturbances such as a roll and a pitch, are detected, and the suspensions are controlled to vary their damping forces in anticipation of impending rolling and pitching motions of the motor vehicle. Therefore, many sensors are required to detect those phenomena. Since the suspension control systems effect predictive control for the operation of the suspensions, necessary arithmetic operations are complex, and the suspensions may sometimes be controlled erroneously to produce damping forces which do not match actual motions of the motor vehicle.
Japanese Laid-Open Patent Publication No. 63(1988)-68413, for example, proposes a suspension control system for controlling the operation of motor vehicle suspensions based on vehicle motion information which is directly detected by a reduced number of sensors.